The invention relates to a selective ion sensitive electrode, and more particularly, to such electrode which may be used to determine the concentration of a specific ion contained in a solution to be examined.
There have been proposed various selective ion sensitive electrodes having an ion sensitive assembly which is selectively sensitive to a specific ion for determining the concentration of the specific ion by comparing a potential developed across an interface between a solution to be examined and the ion sensitive assembly when the latter is immersed into the former with a suitable reference potential. FIG. 1 illustrates an example of conventional selective ion sensitive electrodes. Such electrode is so constructed that a supporter 3 holding an ion exchanger 2 which is selectively sensitive to a specific ion is joined to one end of a stem 1 made from material such as glass, polyvinyl chloride or the like with adhesives 4 such as silicon RTV rubber manufactured by SHINETSU Chemical Co., Ltd. A signal wire 5 formed with coaxial cable has its one end connected to the supporter 3 by passing through the stem 1 and through the medium of an electric conductive resin 6. In the selective ion sensitive electrode thus formed, when the side of ion exchanger 2 which acts as an ion sensitive assembly is immersed into a solution to be examined an interface potential corresponding to the concentration of a specific ion may be developed across an interface between the ion exchanger 2 and the solution to be examined, thereby enabling a determination of the concentration of the specific ion to be made by detecting the interface potential.
However, because such a conventional selective ion sensitive electrode is formed so that the signal wire 5 is connected to supporter 3 or ion exchanger 2 through conductive resin 6, there are disadvantages in that its manufacturing is difficult, the joining strength between signal wire 5 and supporter 3 is small and a mechanical failure often occurs. Therefore an inconvenience is experienced in that stable use over a long term of time can not be expected.